In many electronics applications, such as medical imaging, cellular communication, etc., it is desirable to be able to detect certain signals at low power levels among noise or other unwanted signals. Conventional solutions include logarithmic amplifiers (“log amps”). One characteristic of a log amp is that the output signal is a voltage proportional to the logarithm of the input signal, thereby making the log amp capable of receiving low level input signals and logarithmically amplifying them for output without amplifying the noise or other unwanted signals.
One class of log amps has multiple gain blocks, i.e., amplifiers, cascaded in series to achieve the logarithmic relationship. Due to the serial structure, differences in the performance of individual components tend to have an effect on the overall performance of the log amp. For example, the dynamic range may be limited; that is, the voltage output for very high or very low input signals does not conform to the logarithmic relationship. This can result in erroneous outputs for these extreme input values.